Microspectrophotometry ofEuglena gracilis : Pterin- and flavin-like fluorescence in the paraflagellar body.

The paraflagellar bodies (PFBs) of isolated flagella ofEuglena gracilis were investigated microspectrophotometrically using a visible- and infrared-light microscope with image analyzer and microspectrophotometer. Flagella with attached PFBs were separated from the cell bodies by a short exposure to near-UV light. Fluorescence-emission spectra (excitation at 365 nm) of single PFBs had maxima near 470 and 520 nm, indicating the presence of pterins and flavins. No fluorescence was associated with the flagella themselves. Pterin- and flavin-like fluorescence emission was also found in blue-fluorescing vesicles distributed throughout the entire cell body ofEuglena. Their characterization by microfluorimetry was greatly aided by the use of chlorophyll-free mutants in which the signal-to-noise ratio was distinctly enhanced because of the lack of chlorophyll fluorescence. Our finding of flavin-like fluorescence associated with PFB strengthens similar earlier reports in the literature. The occurrence of pterin-like fluorescence in the PFB lends further support to our earlier proposal that pterins as well as flavins may function as photoreceptor pigments for near-UV and blue light.